feat(ui): ReplyPier 品牌、中文界面与前端构建产物

替换品牌文案与图标，补齐窄屏布局和加载失败提示，确认主要旅程可操作。

frontend/src/assets/telegram-logo.svg

@@ -0,0 +1,12 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 240 240">
+  <defs>
+    <linearGradient id="tg-grad" x1="0.667" y1="0.167" x2="0.417" y2="0.75">
+      <stop offset="0" stop-color="#37aee2"/>
+      <stop offset="1" stop-color="#1e96c8"/>
+    </linearGradient>
+  </defs>
+  <circle cx="120" cy="120" r="120" fill="url(#tg-grad)"/>
+  <path fill="#c8daea" d="M98 175c-3.888 0-3.227-1.468-4.568-5.17L82 132.207 170 80"/>
+  <path fill="#a9c9dd" d="M98 175c3 0 4.325-1.372 6-3l16-15.558-19.958-12.035"/>
+  <path fill="#f6fbfe" d="M100.04 144.41l48.36 35.729c5.519 3.045 9.501 1.468 10.876-5.123l19.685-92.763c2.015-8.08-3.08-11.746-8.36-9.349l-115.59 44.571c-7.89 3.165-7.843 7.567-1.438 9.528l29.663 9.259 68.673-43.325c3.242-1.966 6.218-.91 3.776 1.258"/>
+</svg>